SAW Resonator Authentication for Relay-Resistant Car Entry
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Solution Overview
Problem
Remote keyless entry systems are vulnerable to relay attacks, and existing security measures are not sufficient to prevent unauthorized access or ignition of vehicles.
Innovation Solution
The use of a passive radio, such as a surface acoustic wave (SAW) resonator, in key fobs or smartphones, which requires a precise interrogation signal for activation, making it difficult for attackers to replicate and enhancing security by providing a distinctive resonance response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional active radio systems are used in key fobs, then communication functionality is achieved, but security against relay attacks is insufficient
Solution Approach 1:
The patent employs surface acoustic wave (SAW) resonators that utilize mechanical vibration principles to generate highly frequency-selective responses. When an interrogation signal at the resonant frequency is applied, the SAW resonator vibrates and produces a distinctive ringdown signal that is extremely difficult to replicate, thereby providing robust security against relay attacks while maintaining communication functionality.
Solution Approach 2:
The invention changes the operational parameters of the radio system by using passive SAW resonators with specific resonant frequencies instead of traditional active transmitters. The resonators are designed to respond only to precisely tuned interrogation signals, creating a parameter-based authentication mechanism where the resonant frequency and Q-factor serve as unique identifiers that are difficult to spoof.
2Reliability
If passive radio with SAW resonator is used, then security is enhanced, but device complexity increases
Solution Approach 1:
The patent extracts the active transmission component from the key fob and replaces it with a passive SAW resonator system. The passive radio eliminates the need for batteries, power management circuitry, and active transmission components, significantly reducing device complexity while enhancing security through the inherent properties of the resonator.
Solution Approach 2:
The SAW resonator is a passive component that requires no external power source or control electronics to operate. It automatically responds to interrogation signals at its resonant frequency by generating a distinctive ringdown signal, providing self-service authentication without requiring complex circuitry, microcontrollers, or power management systems.
3Use of energy by moving object
If passive radio is used instead of active radio, then power consumption is reduced, but signal transmission capability is limited
Solution Approach 1:
The passive SAW resonator harvests energy directly from the incoming interrogation signal to generate its response. The resonator's high Q-factor allows it to store and release energy efficiently, creating a detectable ringdown signal without requiring an external power source, thus achieving zero power consumption while maintaining signal transmission capability.
Solution Approach 2:
The system uses periodic interrogation signals from the vehicle to trigger responses from the passive resonator. The resonator is excited periodically by the vehicle's transceiver, and each excitation produces a characteristic ringdown signal that decays over time. This periodic challenge-response mechanism enables reliable communication without continuous power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The passive radio with a high Q factor and distinctive resonance frequency makes it challenging for attackers to launch relay attacks, thereby improving the security and reducing power consumption of the RKE system.
Implementation Method 1
The passive radio may include a surface acoustic wave (SAW) resonator characterized by a distinctive resonance response when prompted to resonate by an interrogation signal
Implementation Method 2
The passive radio is configured to transmit a resonating ringdown signal to the vehicle in response to receiving an interrogation pulse from the vehicle
Data Source
AI summary
Remote keyless entry (RKE) systems and devices are described. The RKE devices include one or more passive radios that respond to an interrogation signal from an interrogating device such as a vehicle. The passive radio sends a responsive signal that can include a decaying portion representing a ringdown signal. The passive radio includes a SAW resonator in some situations.